A Look Back in History: State of California Annual Runoff in Acre Feet per Capita

In the map below, the State of California is sectioned into seven distinct population areas with southwestern portions of the state as an outlier. The map is embedded in a report entitled, “Necessity for the Conservation of the Water Supply of California.” As this report, by J.B. Lippencott, is dated July 1920, it may be presumed that the map is dated at or shortly before 1920.

Annual Runoff in Acre Feet per Capita.

Per Lippencott, “California is divided into a humid section, which is indicated by the green area in the northwestern portion of the state on the map, a semi-humid area which includes the Sacramento Valley and the Coastal Region from San Francisco Bay to Ventura, and an arid section which includes the San Joaquin Valley, the Colorado Delta, and to a less degree the Los Angeles and San Diego coastal plains.”

The report notes that “as compared in population per square mile to Pennsylvania, we [in California] are but 11.2% developed.” And Lippencott extolls the bounty of natural resources of California making a case for immense agricultural expansion, referencing the boom of the rice crops from 1912 onward.

But a reliable source of water is key in achieving this end, and “reliable’ is not a term ably applied to the many waterways in California. To demonstrate this, Lippencott speaks to the seasonal variances of Alameda Creek in Northern California and San Gabriel River in the south of the state.
Of the northern waterway he notes, “On Alameda Creek, which fairly represents the coastal rivers, the annual maximum flow is fifty times the annual minimum flow. These wide variations demonstrate the necessity of holding over water from wet years for those of drought.”

Elsewhere in the report Lippencott states, “Streams of this character [referring to streams with flows of highly seasonal and annual variance] would be immensely enhanced in value if their erratic flow is regulated by storage. Unless there is a practical opportunity for the storage of such waters, their utility is relatively small, but with conservation it at once becomes great.”

Yearly runoffs for various sections of the State identified in the map; from July 1920 Report “Necessity for the Conservation of the Water Supply of California”.

In Lippencott’s lingo, conservation is the act of collection of water by damming rivers and runoff, and by impounding water in underground reservoirs. By these actions it is his intention to conserve water resources that would otherwise drain away “to the sea.” For Lippencott, in a state with so much potential, preserving runoff is the key to growth. In his words, “The measure and the limit of the growth of arid America is the available water supply.”